High performance installation questions

Hi, im moving a Magento 1.9.2 install to a new hosting because it was too slow for our needs.
We have 6000 unique visits per day and transfer around 150GB per month.

We are moving to a single dedicated server with the following specs:
128G Xeon D-1520 Server
HD 2x2TB + 2x300GB SSD

Our plan is to install ESXi 6.0 and partition it in as:

Web server: 1TB HD + 32GB RAM
Gentoo, with nginx and fpm+php with opcode enabled

Cache server: 300GB SSD + 32GB RAM
Varnish with Tupertine plugin

MySQL server: 300GB SSD + 64GB RAM

Backup server: 1TB HD + 4GB RAM.

Is this a good idea? or should i go for a single OS and no ESXi?
Any feedback is welcome!

Cheers,
Roger